Lipid nanoparticles (LNPs) are crucial for delivering nucleic acid therapeutics, yet their complex and heterogeneous nature poses significant challenges for comprehensive quality assessment. Traditional characterization methods provide macroscopic data, failing to offer the molecular-level insights necessary for understanding LNP quality, stability, and in vivo performance. NMR spectroscopy emerges as a powerful, non-destructive tool to bridge this analytical gap. This review highlights the diverse applications of NMR in characterizing LNP formulations. NMR techniques, including solution-state and solid-state NMR, provide atomic-level information on chemical composition, molecular structure, dynamics, and interactions. Specifically, NMR can probe lipid dynamics and molecular organization, revealing how components like cholesterol and helper lipids influence the mobility and arrangement of ionizable lipids. It elucidates the impact of cargo encapsulation on LNP structure, showing how nucleic acids like small interfering RNA (siRNA) interact with and suppress the mobility of LNP constituents. Furthermore, NMR helps understand intermolecular interactions and spatial organization within LNPs, mapping the distribution of lipids and cargo. Finally, NMR can assess the influence of preparation methods on LNP heterogeneity and monitor kinetic processes such as shedding of polyethylene glycol-conjugated lipids. NMR spectroscopy is indispensable for rational LNP design, robust quality control, and ultimately, enhancing the therapeutic efficacy of LNP-based medicines.

Many antimicrobial peptides (AMPs) exert their activity by disrupting the integrity of the bacterial plasma membrane. One of the membrane-disrupting mechanisms of AMPs involves the formation of toroidal pores, composed of α-helices and lipid headgroups. These pores enable the diffusion of lipid molecules to the opposite leaflet without exposing their headgroups to the hydrocarbon core. Consequently, an increase in lipid transbilayer diffusion (flip-flop) in the presence of AMPs is an important characteristic for AMP structure and function. However, real-time monitoring of the rapid flip-flop in the presence of transmembrane pores has not been achieved because of the permeation of membrane-impermeable reagents and/or the low time resolution of the conventional assays. Herein, we have developed a fluorescence quenching-based flip-flop assay. The flip-flop rates obtained by our method were consistent with those measured by the conventional dithionite reduction assay, confirming the reliability of our approach. The real-time monitoring of the flip-flop process in the presence of the AMP, magainin 2, using the self-quenching assay suggested that the disordered toroidal pores composed of 2 magainin molecules facilitate flip-flop. The newly developed assay will provide a better understanding of the interactions between AMPs and lipid bilayers.

The crystal structure and physicochemical properties of loxoprofen sodium dihydrate (LOX-Na 2hyd), a widely used antipyretic analgesic, were investigated. Single crystals were successfully prepared, and their structure was determined via single-crystal X-ray diffraction. The crystals featured alternating hydrophilic and hydrophobic layers: the hydrophilic layer contained water molecules and sodium ions forming coordination and hydrogen bonds, while the hydrophobic layer contained loxoprofen molecules. Thermal analysis revealed that LOX-Na 2hyd desolvated two water molecules at approximately 60°C, dehydrating into an anhydrate without passing through the amorphous state. This anhydrate reabsorbed moisture at approximately 25% relative humidity, reverting to the dihydrate form. Dynamic vapor sorption confirmed the stability of the dihydrate across a wide humidity range. The cyclopentanone ring in the LOX structure exhibited disorder, and crystallographic analysis indicated the coexistence of four stereoisomers (5R, 13R; 5S, 13S; 5R, 13S; 5S, 13R). These findings suggest structural flexibility and potential relevance for optical resolution. Because optical resolution enhances the efficacy of other drugs, such as omeprazole and ofloxacin, this study provides valuable structural insight to support similar applications for LOX. Overall, this work contributes foundational knowledge toward improving the stability and efficacy of LOX formulations through structural and physicochemical understanding.

This paper describes the first total synthesis and absolute configuration revision of biofloranate F, a biflorane-type diterpenoid isolated from the soft coral Lemnalia bournei. The synthesis involved an intramolecular Diels–Alder (IMDA) reaction to form the cis-fused decalin core. A key step was an Evans asymmetric alkylation to introduce an asymmetric center with high stereocontrol while guiding the stereoselectivity of subsequent steps, including the pivotal IMDA reaction. Although the spectroscopic data of the initially synthesized product matched those of the natural compound, its specific rotation was opposite. This discrepancy prompted us to synthesize its enantiomer, which exhibited identical characteristics to those of the natural product. Consequently, the absolute configuration of biofloranate F was unequivocally revised to 5S, 6R, 9S, 10R, and 11S.

Synthesis of 8-membered rings is one of the most challenging transformations in organic chemistry because of entropic hindrance and ring strain. Azocino[4,3-b]indole frameworks are characterized by fused indole–azocane systems and are vital structural components of many natural products and bioactive compounds. We propose a concise and efficient method for constructing these medium-sized rings via Lewis acid-catalyzed intramolecular Friedel–Crafts cyclization of N-(2,2-dimethoxyethyl)sulfonamides. We synthesized cyclization precursors from indolylpropanol derivatives. Treatment of C2-substituted tosyl precursor 4a with catalyst trimethylsilyl trifluoromethanesulfonate (TMSOTf) (0.5 equivalent) at 0°C provided the desired 8-membered product 8a in 96% yield. The mesyl analog 4b is efficiently cyclized to produce 8b and 9b in 77 and 20% yield, respectively. In contrast, the C3-substituted precursor 7a produces the corresponding 8-membered products 10a and 11a in 41 and 23% yield, respectively. The mesyl analog 7b is cyclized to produce 10b at only 20% yield, demonstrating that the tether geometry remarkably affects ring formation. X-ray crystallographic analysis of the elimination product 11a confirms the formation of the fused 8- membered ring system and reveals a distorted boat-chair conformation. This synthesis route provides a mild, chemoselective approach for accessing synthetically valuable indole-fused 8-membered rings, laying the groundwork for future development of natural product derivatives and functionalized analogs.

For the production of active pharmaceutical ingredients through sustainable organic synthesis, the use of inexpensive and non-toxic catalysts is desirable. Recently, homogeneous chiral Fe catalysts have received considerable attention as tools for achieving this goal. However, chiral Fe catalysts often perform poorly when used to synthesize complex molecules, limiting their application to large-scale syntheses. In this study, we developed an asymmetric sulfoxidation reaction for the production of esomeprazole at a pilot-plant scale. The reaction uses a catalytic system generated in situ from an Fe salt, which is abundant, inexpensive, and environmentally friendly, combined with a chiral Schiff ligand and a carboxylate salt, and hydrogen peroxide as the oxidant. Subsequently, the obtained esomeprazole is converted from its K-salt form to an Mg-salt, thereby establishing a manufacturing process that yields high-purity active pharmaceutical ingredients with impurities controlled to less than 0.05%. The enantioselectivity and kinetic resolution of the asymmetric sulfoxidation reaction are dependent on the spatial relationship between the sp³-hybridization center and the sp² carbon adjacent to the substituent attached to the S atom of the substrate. We also speculate that the carboxylic acid additive plays a critical role in activating hydrogen peroxide through heterolytic cleavage and enabling the formation of both mono- and dinuclear iron oxidants. Furthermore, we propose a catalytic mechanism for this enantioselective oxidation reaction.

1,3-Dipolar cycloaddition reaction of stable nitrile oxides with α,β-alkynyl hydrazones affords 5-iminoisoxazoles, whereas the reaction of nitrile oxides with α,β-alkynyl carbonyl compounds gives 4-acylisoxazoles. The regioselectivity of the cycloaddition reaction is reversed due to the electron-donating character of the hydrazone group. The 5-iminoisoxazoles are readily converted to the corresponding 4-acylisoxazoles by dehydrazonation.

Three new acylated glycosidic acid methyl esters and one known compound were isolated by treating the crude resin glycoside fraction derived from the seeds of Ipomoea lacunosa with indium(III) chloride in methanol, and their structures were elucidated using spectroscopic methods. The new compounds contained methyl 3S,11S-dihydroxytetradecanoate as the aglycone. Two were hexaglycosides and one was a nonaglycoside, with saccharide cores partially acylated by a glycosidic acid, 7S-hydroxydecanoic acid 7-O-β-d-quinovopyranoside (quamoclinic acid B), and/or organic acids, including isobutyric and 2S-methylbutyric acids. Furthermore, the cytotoxic activities of the isolated compounds against HL-60 human promyelocytic leukemia cells were evaluated, and they exhibited moderate activities.

Lysosome-targeting chimera (LYTAC) efficiently degrades specific membrane proteins. In a previous study, we synthesized and reported human epidermal growth factor receptor 2 (HER2)-LYTAC (that induces the degradation of HER2 protein using DNA aptamers that binds to insulin-like growth factor receptor 2 and HER2). In this study, we designed and synthesized linker-length-modified HER2-LYTAC derivatives with varying distances between the DNA aptamers and assessed their protein degradation-inducing activity. The results revealed that HER2 degradation varied significantly with the linker length. Notably, HL5L—HER2-LYTAC with a 5-bp longer linker than that of the original HER2-LYTAC—exhibited equivalent or enhanced activity and significantly inhibited the proliferation of HER2-positive cancer cells. This is the first study to assess the effect of linker length in designing LYTAC molecules using bispecific DNA aptamers and offers valuable insights into the molecular design of nucleic acid-based LYTACs.